source of earth's gravity...

[Mart]

mass and energy are the same thing

 

I thought mass and energy are two aspects of the same thing.

[Ophiolite]

I woud say all three of these statements are valid.

 

mass and energy are the same thing

mass and energy are two aspects of the same thing

mass and energy are two different things

 

It depends upon context, perspective and purpose..

[Mart]

I woud say all three of these statements are valid.

 

mass and energy are the same thing

mass and energy are two aspects of the same thing

mass and energy are two different things

 

It depends upon context' date=' perspective and purpose..[/quote']

 

Think about something less esoteric like the mass and volume of a substance. They can be represented mathematically by volume = constant times mass which is the same form (mathematically) as energy = constant times mass. Now I don't confuse the mass of a substance with the volume of a substance so why should I make mass and energy identical?

[Ophiolite]

because I can transform mass into energy and vice versa

[Mart]

Scientific theories have to do more than explain - they have to predict.

 

I agree. Theories that can explain but can't predict and theories that can predict but can't expalin aren't scientific.

[Mart]

because I can transform mass into energy and [i']vice versa[/i]

 

 

So how would you transform mass into volume? And if it can't be done what is the significance of the same mathematical structure representing the two quite different relationships.

[Sayonara]

I don't recall Ophiolite making any claims about volume...?

[Ophiolite]

So how would you transform[/i'] mass into volume? And if it can't be done what is the significance of the same mathematical structure representing the two quite different relationships.

You also said

volume = constant times mass

energy = constant times mass.

 

I would add

wages = constant times hours worked

 

It's a common form.

 

I'm not sure what you are asking..,,,,,,,

[Mart]

I don't recall Ophiolite making any claims about volume...?

 

Ophiolite didn't. I was asking this : if energy = mass * constant is the mathematical form of the relationship that Einstein wrote down and if from this he reasoned "therefore I can transform energy into mass" why can't the same reasoning be applied with any mathematical relationship that has the same form . I used volume = mass * constant for a substance and asked why can't the volume of something be tranformed into its mass.

[Mart]

You also said

volume = constant times mass

energy = constant times mass.

 

I would add

wages = constant times hours worked

 

It's a common form.

 

I'm not sure what you are asking..' date=',,,,,,[/quote']

 

I think my point is that wages are not the same as hours worked. Therefore mass is not the same as energy

[Sayonara]

In both cases the relationship seems to be one of equivalency.

[Mart]

In both cases the relationship seems to be one of equivalency.

 

Yes, an equals sign in an equation leads one to expect some form of equivalency. Can you explain further?

[Ophiolite]

if energy = mass * constant is the mathematical form of the relationship that Einstein wrote down and if from this he reasoned "therefore I can transform energy into mass" .

I believe you may have this back to front. Surely Einstein first postulated the equivalence, and mutability, of energy and matter, then asked 'how are they related'....

[Mart]

I believe you may have this back to front. Surely Einstein first postulated the equivalence, and mutability, of energy and matter, then asked 'how are they related'....

 

That sounds interesting. Do you have a source? It'll save me hunting round for it.

[Sayonara]

Yes, an equals sign in an equation leads one to expect some form of equivalency. Can you explain further?

I'm not sure exactly where the problem lies.

[Ophiolite]

That sounds interesting. Do you have a source? It'll save me hunting round for it.

No. When I qualify a statement with 'I believe' I am generally indicating that this is my understanding, but that I am not confident I am correct. I hope (a hope that is generally realised) that if I am wrong a more knowledgeable person will correct me.

You may wish to go straight to source. This is Einstein's own popular account of his work.http://www.bartleby.com/173/

[JaKiri]

It's because, when you're talking about changing energy into mass and vice versa, the equation in question is (delta)E = (delta)mc^2.

 

No such equation exists for mass and volume; E=mc^2 doesn't mean that mass can be changed into energy per se, just like volume = mass / density doesnt' mean that volume can be changed into mass.

[Mart]

It's because' date=' when you're talking about changing energy into mass and vice versa, the equation in question is (delta)E = (delta)mc^2.

[/quote']

 

But that doesn't help me because it's still a change in mass or a change in energy and I don't understand how mass and energy are the same stuff.

 

Let me put it another way. Frequency and wavelength are two aspects of a wave. The names frequency and wavelength stand for qualities of the wave which we are interested in. In particular we want to know in what way the numerical value of these two qualities are related. Put in computing terms frequency and wavelength are exactly like the names of two variables. But the names of the variables should not be confused with the values of the variables.

[JaKiri]

Frequency and wavelength are two aspects of a wave.

 

Mass and (any given other form of energy, for example, kinetic or gravitational) are two aspects of 'energy' entire.

[Mart]

Mass and (any given other form of energy, for example, kinetic or gravitational) are two aspects of 'energy' entire.

 

OK.

If I change the word 'energy' into ? then that's answered my question. Thanks.

[swansont]

E=mc^2 doesn't mean that mass can be changed into energy per se

 

That's a very important point.

 

It's the fact that we can do reactions that change a system's energy that cause the mass to changes. The equation itself doesn't guarantee it. It's the existence of forces between particles that allow the energy of the system to change.

[Mart]

That's a very important point.

 

It's the fact that we can do reactions that change a system's energy that cause the mass to changes. The equation itself doesn't guarantee it. It's the existence of forces between particles that allow the energy of the system to change.

 

How does the existence of forces between particles allow the energy of a system to change?

[JaKiri]

How does the existence of forces between particles allow the energy of a system to change?

 

Forces and energies are connected at a fundamental level. One is the integrated other, with respect to displacement.

[Mart]

Forces and energies are connected at a fundamental level. One is the integrated other, with respect to displacement.

 

Can you explain further? It sounds a bit esoteric.

[swansont]

F = -grad(U) for conservative forces. U is potential energy.